There is an ongoing discussion in the reftypes proposal about whether funcref is a subtype of anyref. A consequence of this is another discussion about whether ref.null encodes a nulltype that's a subtype of all nullable reference types, or carries a type that designates the type of null that's encoded (eg, ref.null func would be type null<func> or maybe just the type funcref, depending).

This dicussion obviously blocks reftypes from shipping.

This discussion also blocks bulk memory from shipping because it affects the encoding of initialization expressions in element segments: they can currently be ref.func $f or ref.null, but the null encoding may need to change, and we can't ship until that's settled.

The discussion has been finalized, we're severing the subtyping relationship between funcref and anyref, and ref.null and ref.is_null become parameterized instructions.